Composition for cadmium plating baths



Patented Nov. 24, 1931 UNITED STATES PATENT OFFICE cm 11:. HUMIHRIES, or INDIANAIBOLIS, INDIANA, AssIeNoB 'ro minus 0. I'A'MEN.

or INmANAroLIs, INDIANA; n. max MoKINNEY, SPECIAL ADMINISTRATOR for 88.11) JAMEQ C. PATTEN, DECEASED COMPOSITION FOR GADMIUM PLATING BATES Ho Drawing.

In my applications pending in the Patent Oflice, Serial Nos. 257,152, 267,273 and 221,619, I have described a certain type of lating bath which is acid and from which a ne, smooth, homogeneous, continuous coat of bright cadmium can be deposited.

It is the object of the present application to provide an improvement or a modification of the composition described in said above mentioned applications.

Plating baths vary in composition and also in throwmg power, which latter term is the platers term covering the readiness or lack of readiness with which a metal from a given solution tends to throw-into recesses or deep holes. Some plating solutions .have this throwing power property to a marked extent, while others, such as for instance, the average chromium plating solution has this pro erty to a very limited extent. The greator the throwing power of a plating solution, the more even is the deposit of the metal from such solution all over the surface of the article to be plated. Hence -the neces- 'sity for improving the throwing power of any plating solution.

In this application-now described, I have modified the formulae from that set forth in said applications with this point in view,

and have improved this type of acid cadmium plating bath.

In general, acid cadmium plating solutions do not have as high a throwing power as a cyanide plating solution of the same metal,

and in some cases are not employed to plate various articles, for that reason. In the bath of this application the throwing power is quite high. A suitable formula is now 0 given for a still solution, per gallon of water 8 oz. H280 used 4 oz: A1 sol) .12H 0 10 oz. ...so.1oH,o

.8 oz. CdO or 2.8 oz. C(HOH), or 8.1 oz. CdCO 10 g. glue The bath using this formula can be made in one or two ways, and description is here glven of two methods for maklng up a platmg bath of this formula.

Add cadmium salt whlch can be hydrate.

do oxide or carbonate. Add to the above about Present per gal. 1% oz. free B 80;

' 3.1 oz. 060 or Appllcatlon filed October 1, 1828. Serial No. 309,694.

half a gallon of water, containing enough sulphuric acid to react with the cadmium salt,

plus a definite amount of free sulphuric acid, whichcan be from to 1 oz. per gallon.

To another half gallon of water is added the other salts which can be sodium sulphate, ammonium sulphate or aluminum sulphate. The two are then mixed. After mixing about a pint of this solution is removed an then there is dissolved the brightening agent, which can be glue, for example. This is done by heating this pint of solution and adding ing the glue is then added to the remainder of the bath. The solution then contains the cadmium salt and some free acid and the other salts which actas agents for improving the throwing power, with the exception of the aluminum sulphate which is to tend to make a whiter deposit of cadmium. The glue acts as the brightening agent.

I do not limit myself to the use of glue alone as a brightening agent, but can use isinglass agar agar or glucose.

When such a plating bath is used,-cadmium anodes of the purity, such as is found in.

I prefer to use somewhat difi'erent concentraa tions, and below is given the formula for such a bath. 1 z A1 d 1213. 0 18. 'oz. 21 sdgiarizo S 1 Present er 3.5 oz. Cd 6H), or

3.5 oz. coco. 10 g. glue In place of using the above described method of making up such solution, I can if I wish, employ a mixture of the dry salts included in this formula, dissolving them in the glue and stirring. The solution contain- I gal. 3.5 015. free H 8 approximately hot water and stirring them. They are then readily soluble and form a constant composition. In making the bath initially, there is a tendency for some of the aluminum sulphate of commerce, to give the bath a milky appearance, but after using for a little time,

c this milky appearance disappears. During this milky period, there is 2 tendency for some of the glue to settle out, but after .the

milkiness has disappeared this condition is" not found.

Brightening agents of the types indicated have a tendency to slowly come out of the bath and be co deposited with the cadmium, but they can be added in lesser quantities than as shown in the formula, when evidence of their elimination is indicated by diminishing brightness.

It will be necessary from time to time to scrub the anodes, as they become slightly filmed, particularly while standing. But this is not a great difliculty and is commercial plating room practice for other types of platcan be used without any harm to a barrel plating solution.

. Current densities in the still baths are between 10 and 20 amperes per sq. ft, the usual rang? being between 12 and 15 amperes per sq. Above these current densities, there is a tendenc for the color of the. deposit to change an to become duller and if considerably hi her current densities are used,

there will treeing. I

, In barrel plating solutions,-.the barrel parts should not be made of iron or steel, as is sometimes used, but should beof brass, toprevent the dissolution of the iron in'this solution.

Coats of desirable thickness for proper protection on iron and steel articles can be I claim as my invention:

1. A composition of matter adapted forus'e in forming an acid solution for the electrodeposition ofcadmium consisting of substantially' three ounces of sulphuric acid, two to eight ounces of aluminum sulphate, ten to twenty ounces of sodium sulphate, two to five ounces of cadmium salts containing oxygen and ten grams of a brightener.

2. A composition of matter adapted for use in forming an acid solution for the electrodeposition of cadmium consisting of substantially three ounces of sulphuric acid, two to eight ounces of aluminum sulphate, ten to twenty ounces of sodium sulphate, two to ten ounces of ammonium sulphate, two to five ounces of cadmium salts containing oxygen and ten grams of a brightener.

3. A composition of matter adapted for use in forming an acid solution forthe electrodeposition of cadmium consisting of substantially three ounces of sulphuric acid, two to eight ounces of aluminum sulphate, ten to twenty ounces of sodium sulphate, two to five ounces of cadmium oxide, and ten grams of a brightener.

4. A composition of matter adapted for use in forming an acid solution for the electrodeposition of cadmium consisting of substantially three ounces of sulphuric acid, two to elght ounces of aluminum sulphate, ten to twenty ounces of sodium sulphate, two to ten ounces of ammonium sulphate, two to five ounces of cadmium oxide and ten grams of a brightener. In witness whereof, I have hereunto set my hand at Arlington, N. J this 22nd day of September, A. D. one thousand nine hun- 4 dred and twent '-ei ht. V

HED H. HUMPHRIES.

obtained in a smooth form from these solu- -The-bath which I have above described may be prepared in dry salts form for shipment to the plant, and as an aid in maintaining constancy of composition.

There can be some slight increase or de-- crease from the composltion given for the three added salts, -.namely ammonium sulphate, aluminum sulphate and sodium sulphate.

There can also be some variation from the "cadmium metal content and the free acid con- 5 tent indicated. I can for example vary the aluminum sulphate content from 2 to 8 oz.;

sodium sulphate from 10 to 20 .oz. and ammonium sulphate from 2 to 10 oz. 

